Estimation of Quantization Step Size Against Amplitude Modification Attack in Scalar Quantization-Based Audio Watermarking

Scalar quantization-based watermarking schemes are very vulnerable to amplitude modification attack. To overcome this problem, we propose a novel and robust algorithm that estimates the modified quantization step size by searching QE (quantization error) function. For efficient searching of QE curve, we analyze the peak curve of QE analytically and derive the equations to determine an appropriate search interval. The search interval can be determined from the mean and variance of an audio signal regardless of its probability density function shape. The experimental results demonstrate that the proposed algorithm provides both exact estimation of the modified quantization step size and good watermark detection performance under AWGN attack